Engineered wood products such as oriented strand board (OSB) and particle board are made by adhering together fragments of wood. The properties of the resulting materials depend significantly upon the way in which the fragments are aligned with one another as well as the orientations of fibers within the fragments of wood.
The strength properties of many composite fibrous materials are sub-optimal in cases where fibers in the materials are arranged so that the fibers are preferentially aligned in one direction. For example, in OSB, if adjacent layers of wood chips are not aligned with grain extending perpendicularly to one another then the mechanical strength of the OSB will be reduced. Similarly, the orientation of fibers in paper can affect mechanical characteristics of the paper. In making composite fibrous products such as OSB or paper it would be desirable to have a way to evaluate whether fibers in the products are arranged optimally or not.
There are various ways to measure fiber orientations. Some of these are as follows:                One can dissect samples of a material under a microscope. This is not a practical method for process control.        One can measure DC or low-frequency AC dielectric constants of the material. The dielectric constant perpendicular to the wood grain is known to be different from the dielectric constant parallel to the wood grain. It is not practical to use measurements of dielectric constant for process control because measuring the dielectric constant of a material is typically too slow and also requires contact with the material in most cases.        Optical methods can be used to determine fiber orientation but these methods can only determine the orientation of fibers at the surface of the material.        X-ray analysis may be performed, however the equipment required for X-ray analysis is expensive and there are safety issues with X-rays. P. H. Friedlander “The measurement of fiber orientation in newsprint with respect to the machine direction by X-ray diffraction” Pulp and Paper Magazine of Canada, June 1958, pp. 102-103 and H. Ruck et al., “The determination of the fiber orientation in paper” Pulp and Paper Magazine of Canada, June 1958, pp. 183-190 disclose the use of X-ray diffraction to monitor fiber orientation in paper.        U.S. Pat. No. 4,654,529 entitled “Method for measuring the fiber orientation anisotropy in a fibrous structure” discloses a method for evaluating the fiber alignment anisotropy in a fibrous structure by measuring attenuation as a function of polarization        
There is a need for technology that can be used to determine fiber orientation and/or the degree of anisotropy in fiber orientation in composite fibrous materials. There is a particular need for such technology that can be applied in industrial settings.